1. Technical Field
The present invention relates to a glossing device and an image forming apparatus incorporating the same, and more particularly, to a glossing device for imparting gloss to a toner image formed on a recording medium, and an image forming apparatus, such as a photocopier, facsimile machine, printer, plotter, or multifunctional machine incorporating several of these features, incorporating the glossing device.
2. Background Art
Glossing devices are employed in image forming apparatuses, such as a photocopier, facsimile machine, printer, plotter, or multifunctional machine incorporating several of these features, where a toner image formed on a recording medium, such as a sheet of paper, is processed with heat and pressure to obtain a resulting print with a high gloss finish. The glossing process is one of several features incorporated in image forming apparatuses, particularly in color printers, where higher levels of gloss are required than those provided in monochrome printers.
Some glossing devices employ a belt-based assembly including a looped, endless belt entrained around a heat roller and other belt-support rollers, and a pressure member disposed opposite the heat roller to press against the heat roller via the belt to form a glossing nip therebetween, through which the recording sheet passes. The endless belt is equipped with a belt cooler, such as a heat sink, disposed inside the loop of the belt to cool the belt during movement downstream from the glossing nip.
During operation, the recording sheet enters the glossing device after passing through a fixing nip where the toner image is fixed in place with heat and pressure. At the glossing nip, heat and pressure applied to the recording sheet transforms the once-fixed toner image into a molten, adhesive state that exhibits adhesion to the conveyance surface of the belt, so that the toner image, which is cooled to solidify while conforming to the conveyance surface of the belt downstream from the glossing nip, assumes a smooth, glossy appearance.
Various types of belt-based glossing devices are known in the art. For example, one such technique employs a single endless belt to define a conveyance surface on which the recording medium is conveyed with its printed face directed downward. A belt cooler is disposed adjacent to the endless belt moving downstream from the glossing nip, such that the recording sheet during conveyance faces the belt cooler via the belt therebelow.
Another technique employs a pair of opposed, endless belts, one upper and the other lower, to define a conveyance path therebetween along which the recording medium is conveyed with its printed face directed upward. A belt cooler is disposed adjacent to the upper one of the paired endless belts moving downstream from the glossing nip, such that the recording sheet during conveyance faces the belt cooler via the belt thereabove.
The inventors have recognized that one problem associated with a glossing device employing an endless belt assembly with a belt cooler is that the belt occasionally separates from the belt cooler due to loosening or slackening of the belt. Separation of the belt from the belt cooler, if not corrected, would result in reduced cooling efficiency with the belt cooler and concomitant degradation of imaging performance of the glossing device.